fix a small typo
diff --git a/Doc/library/subprocess.rst b/Doc/library/subprocess.rst
index 1e1f03e..42e50f6 100644
--- a/Doc/library/subprocess.rst
+++ b/Doc/library/subprocess.rst
@@ -318,8 +318,8 @@
    output = Popen(["mycmd", "myarg"], stdout=PIPE).communicate()[0]
 
 
-Replacing shell pipe line
-^^^^^^^^^^^^^^^^^^^^^^^^^
+Replacing shell pipeline
+^^^^^^^^^^^^^^^^^^^^^^^^
 
 ::